Gender prediction!

On Wednesday, Kyle and I are going to my 20 week ultrasound and we'll find out if we're having a boy or a girl. So we decided to do put some old wives' tales to the test! We based our tests on research and results from this blog. She and I were in the same major (Political Science) and I really got to know her in our awesome political economy of women class and capstone class. I also thoroughly enjoyed their statistical analysis. We did different tests because we didn't agree with some they used and we've already had some predictions made. So here goes:

The Tests
1. Pencil on a string (circle=boy, back and forth=girl): GIRL
2. Heartbeat (under 140=boy, above 140=girl): GIRL
3. Genetics (based on Kyle's nieces and nephews): BOY
4. Ancient Chinese Prediction Method (Age at conception + Month of conception): BOY
5. Ancient Mayan Prediction Method (Age and Year of conception are both even or odd=girl, not the same=boy): BOY
6. How a key is picked up (narrow part=girl, round part=boy): GIRL
7. Pregnancy acne (normal=boy, worse=girl): BOY
8. Swinging wedding ring (circle=boy, back and forth=girl): GIRL
9. Morning sickness in first trimester (bad=girl, little or none=boy): BOY
10. How baby weight is carried (hips=girl, tummy=boy): BOY

(copied from blog)
Our Analysis
"We decided to use a weighted average of our ten-dimensional vector to statistically combine the results of all ten tests. The weights are a number between 1 and 0 that conveys how much we trust that particular measure (1 = perfect trust, 0 = no trust whatsoever). The vector of predictions (Vp) is first assembled thus (1 = girl, -1 = boy)":

[1, 1, -1, -1, -1, 1, -1, 1, -1, -1]

 Our trust values are chosen based on the following reasons:
1. We trust this one a lot. Our friend Dennis performed this test on his wife and friends and has been right every time. Trust = .98
2. We found studies that disprove this test and that heart rate is based more closely on the baby's birth weight. However, the study found that boys tend to be heavier than girls and thus have a lower heart rate, though it is possible to have a heavy girl and vice versa. Trust = .65
3. Genetics are pretty hard to argue with. Of Kyle's 6 biological niblings, 5 are boys and 1 is a girl. But surprises can happen! Trust = .87
4. While ancient methods are tried and true, Chinese culture tends to be more biased toward boys. Trust = .75
5. Again, ancient methods are tried and true, and this researcher has no knowledge of ancient Mayan biases. Trust = .93
6. Not a lot of trust in this test as results depend upon too many variables (e.g. weight and size of key, direction key is pointing, etc.). Trust = .2
7. This is preposterous; girls should make your skin glow. Trust = .2
8. Unlike the pencil on a string, we could not get a good reading on this test. Trust = .01
9. This is also somewhat unfounded. The foreign entity of the boy fetus should make me sicker. And, as was said on the other blog, "Girls don't make me barfy. This is simply absurd." Trust = .1
10. No opinion on this test. Trust is a neutral .5

Trust vector (Vt):

[.98, .65, .87, .75, .93, .2, .2, .01, .1, .5]

Final weighted average =

Vp * Vt / 10 = -0.151

-0.151 < 0

So we might be having a BOY. We'll see how accurate our prediction is on Wednesday. Kyle anticipates this method becoming more accurate with the more children we have as we weed out the inaccurate tests. Stay tuned! We're so excited (read: Kyle is curious and I'm antsy)!